Typical pulsed radar altimeters determine an aircraft's altitude by measuring time from a transmitter radio frequency (RF) pulse to a receiver pulse signal reflected from the ground. In “mission-critical” avionic navigation systems, for example, the aircraft includes more than one pulsed radar altimeter for redundancy. For proper redundant navigation, a primary radar altimeter is configured to reject the reflected ground return signal from a second, companion radar altimeter.
However, when at least two transmitted RF signals from at least two pulsed radar altimeters are present, current redundant radar altimetry configurations do not always distinguish the receiver pulse signal for the primary radar altimeter from that of the companion radar altimeter. Consequently, the measured altitude has errors caused by these conflicting receiver pulse signals, and within a relatively short period of time the radar transmissions become jammed and ineffective. Moreover, the randomized time interval can become a repetitive sequence, similarly rendering the radar transmissions as being ineffective for navigation purposes.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for methods of pseudo-random pulse interval generation in navigation-aiding devices.